During the trials, the second T-50-2 prototype, along with a Su-25UB trainer/strike aircraft, successfully approached an Il-78 refuelling tanker, reports RIA Novosti.

As part of a wide range of flight trials, the T-50-2 is currently being tested for its flight envelope under regimes such as subsonic and supersonic as well as in various configurations.

Developed under Moscow’s Future Aviation System for Tactical Air Force (PAK FA) programme, the Sukhoi T-50 is a twin-engine jet fighter that will be the successor to Russia’s fleet of MiG-29 Fulcrum and Su-27 Flanker aircraft.

Equipped with radar-evading stealth technology, the multirole fighter aircraft is designed to conduct supersonic flights at speeds of over 2,000km/h and participate in in-flight refuelling missions.

Powered by two Saturn-Lyulka 117S turbofan engines, the 18,500kg aircraft also features short take-off and landing capabilities, and is capable of achieving a low radar visibility and heat signature.

Conducting its initial flight in January 2010, three prototypes of the T-50 have undergone flight tests, while the fourth is expected to undergo testing later this year.

Currently, the first T-50-1 prototype is being readied for flight trials at "super-critical angles of attack and super-manoeuvrability", while the third T-50 prototype has recently demonstrated performance of its new onboard X-band active phased array radar system.

The aircraft is expected to enter operational service with the air force in 2015 as the country’s first new military aircraft since the fall of the Soviet Union.